The present invention relates generally to the technical field of solid-state conductors, and, more specifically, relates to sodium ion solid-state conductors.
As energy storage requirements become more demanding, next generation devices will require a multitude of high performance battery products. Electrochemical energy storage is required for grid storage, wireless communications, portable computing, and will be essential for the realization of future fleets of electric and hybrid electric vehicles.
Application areas, such as clean and renewable power, depend on new battery technology for longer cycle life, higher energy densities, better recharge ability and increased reliability. In addition, there will always be an environmental concern during production and use regarding safety and recycling. Further, since electrolytes in a battery conduct ions, block electrons, and separate the electrodes to prevent shorting, the electrolytes are an important part of a battery, and the development of high performance electrolytes will be significant for efficient battery technology, enhancement and broad applications.
Some batteries currently available use a liquid electrolyte containing a flammable organic solvent. As such, they require installation of a safety device to inhibit the temperature rise at the time of short circuit or improvement in technical structure or materials to inhibit short circuit. In contrast, a battery having a solid material can avoid this flammable solvent problem, and thereby simplify the safety device and reduce production cost and productivity.
Solid-state conductors that possess high ionic conductivity are needed for a broad range of electronic and power applications. Applications now also may include chemical sensors, transistors, electromechanical actuators, and light-emitting electrochemical cells. For some applications, it is desirable to incorporate high ionic conductivity while maintaining certain mechanical properties. In looking at those possible materials that can be used for conductors in these electrochemical energy conversion and storage systems, various candidates have appeared. However, the state of the art considers materials that are of limited availability, are expensive, or whose chemical processing is not environmentally green.
For future applications, new solid-state materials with high ionic (lithium and sodium) conductivities are needed. Specifically, for sodium ion batteries there are only few materials available that are good candidates to replace the liquid electrolyte. Most recognize the major class of solid-state sodium ion conductors as NASICON. These materials are based on Na—Zr—Si—P—O-based composite oxide, with the possibility of doping NASICON structures with Fe. However, these materials have the drawback of being reactive with metallic sodium. Thus, there is need for a different class of materials.